I have to assess that someone who tends to be irresponsible and doesn't fulfill their duty is more likely an FP type than an TJ/TP.
TJ people tend to be motivated by a sense of DUTY- so they will do something if they gave their word to do it- FPs- on the other hand, will do as they see fit, and if they're in a "bad mood" won't come through with the goods, even if they say they will do it.
Blowing off duties and being flakey is a big deal- and often when there are numerous institutions involved and multiple people on call- usually the FPs are the ones who are the most unreliable, I have found. TJs- even if they are sick and their dog just died, will find the time to do what they were asked to do.
This has other connotations as well- being that FPs tend to be more spontaneous, etc- but usually anyone just blowing off something they were asked to do- screams FP to me, and most of the time I've found- are ENFPs.
ESFPs like social decorum so will do their best anyway, even if they don't "feel" like it.
Same with ISFPs.
INFPs will do something they find tedious because they see the potential in long-term relationships. Occasionally when something of a personal nature comes up- they let you know in advance being that they are introspective and conscious about seeming like flakes.
ENFPs on the other hand- will cancel at the last minute, never do what they were asked to do, and often use the excuse of their personal illness- or their dog/neighbor/family member dying to get out of something RIGHT before the deadline, if AT ALL!
I can't think of the multiple instances in which I left an ENFP in charge of something, and she/he would say he would do it- but then NEVER DO IT!
Anyway, just saying Alicia- if this woman is flakey, chances are, she is an ENFP.
(OK, all ENFPs can comment on this as well- but gotta admit- TJs are very conscientious about giving people enough time esp. if they cancel on something they were expected to do)